Other Income and Other Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Other income:
Interest income	$ 2,694	$ 1,957	$ 7,695	$ 6,256
Miscellaneous	22	91	50	95
Total other income	15,191	6,958	35,245	17,541
Other expense:
Non-operating costs	(2,647)	(2,480)	(8,832)	(7,404)
Investment losses — net	(716)	0	(1,445)	(268)
Miscellaneous	(2,377)	(2,583)	(4,171)	(4,391)
Total other expense	(5,740)	(5,063)	(14,448)	(12,063)
APS
Other income:
Interest income	2,037	1,151	5,091	4,874
Miscellaneous	22	92	50	96
Total other income	14,534	6,153	32,641	16,160
Other expense:
Non-operating costs	(2,448)	(2,334)	(7,965)	(6,931)
Miscellaneous	(378)	(1,027)	(2,167)	(2,748)
Total other expense	(2,826)	(3,361)	(10,132)	(9,679)
SCR deferral
Other income:
Debt return on Four Corners SCR (Note 4)	4,920	4,910	14,651	11,190
SCR deferral | APS
Other income:
Debt return on Four Corners SCR (Note 4)	4,920	4,910	14,651	11,190
Ocotillo deferral
Other income:
Debt return on Four Corners SCR (Note 4)	7,555	0	12,849	0
Ocotillo deferral | APS
Other income:
Debt return on Four Corners SCR (Note 4)	$ 7,555	$ 0	$ 12,849	$ 0